Railroads are important transportation systems for moving freight. When a freight train enters a major rail yard it must be broken down and the cars must be redistributed to new trains going to different destinations. The procedure for breaking down trains is labor intensive, dangerous, and time consuming and takes place in railroad “yards.” Federal Railroad Administration (“FRA”) statistics show that between 1994 and 1998 more than 6,400 accidents took place in railroad yards. Of these accidents, approximately 75 resulted in fatalities. Of these accidents 60% were associated with problems with switches and switching. Further, the labor intensive process adds a great deal of dwell time to the operation causing extended time lapses between train arrival and departure.
Railroad locations that process a number of railroad cars daily are generally referred to as “yards”, which process from 50 to perhaps as many as 1500 cars per day. Many of these cars carry railroad containers. Railroad cars which carry two containers are called “double-stacks” because they carry containers that are stacked on top of each other.
Trains arrive at a railroad yard daily from outlying locations to the yard. The purpose of a railroad yard is to switch, or sort, rail cars so that they may be assembled into trains going to another yard at a new location. Cars in inbound trains to the yard are mixed up. For example, a train inbound to a yard in Columbia, S.C., may be carrying railroad cars that have ultimate destinations, such as Charlotte, N.C., Atlanta, Ga., Jacksonville, Fla., Kansas City, Mo., St. Louis, Mo., etc.
Each car in the inbound train must be sorted and put into the proper railroad track so that it can continue to travel to its ultimate destination on another train, much as passengers change planes in New York or Atlanta go from one plane to another to reach their destination.
The process takes place generally as follows. A train arrives at a rail yard and is “yarded” (stops) in a “receiving” yard track. The locomotive power is detached (uncoupled) from the rail cars, and proceeds to the locomotive engine service facility. Meanwhile, the train must be “bled” of its air, so that the rail cars can roll freely. When trains depart railroad terminals, the air lines between each car are pumped full of air, about 75 psi. When the air in the train line is pumped up, all of the brakes on the rail cars are released. When this occurs, metal or composite brake shoes on each rail car come away from contact with the wheels of each rail car. At that point cars will roll freely. After the train is bled, the cars can be classified; i.e., rolled to the proper track for their outgoing destination. There are three typical ways to perform this process.                1. The rail cars are shoved to their proper class track by a locomotive(s). Once in their proper class track, the rail cars are “uncoupled” from the locomotive(s) or other rail cars ahead of them. “Uncoupling” is performed by a person on the ground who operates the mechanical uncoupling lever which is a mechanism on the side and end of each rail car.        2. The rail cars are catapulted to their proper track by revving up the speed of the locomotive(s) and by throwing switches which guide each car to its proper track. The switches are thrown by people on the ground who shunt the switches properly.        3. The rail cars are shoved up to the apex of a hill, and are separated at the apex by people who uncouple the cars. From the apex, the cars roll freely by gravity and are guided by switches which are automatically thrown by mechanical devices that are activated by a computer program to guide them to their proper track in the classification yard. This is referred to as a “hump” yard.        
U.S. Pat. No. 3,727,559 describes an automated control system for the track switches on the hump tracks of a two-section classification yard having two inlet hump tracks interconnected by a cross-over, allowing manually controlled and automated routing of cars from each hump track to any destination track in either section of the yard. This system uses a hump and switches to control car classification from two humps.
In U.S. Pat. No. 3,865,042, a method and apparatus for controlling the positioning of switches in a railway classification yard is described to route to their respective destination tracks successive cuts from a train, as they are uncoupled at the hump of the yard. As described, a computer receives information respecting the location of the various cuts as they are traveling through the yard and operates the various switches in the yard to route each of the cuts to its destination track. This system uses a method and apparatus for controlling the position of switches in a railway classification yard so as to route successive cuts from an incoming train to designated tracks in the classification yard. This is a gravity system and requires switches to function.
U.S. Pat. No. 4,610,206 describes a modular control system for railroad classification. As described, the control system can automatically perform those functions necessary to control various elements of a railroad classification yard to enable the train of cars to be switched from a hump track to one of a plurality of bowl tracks in accord with the destination for the car. This is a modular control system that is used in conjunction with a hump and switches.
In U.S. Pat. No. 4,487,547, a car positioning device is described for dumping of random cars in a rotary dumper, and a method for directly positioning cars within a rotary dumper, where the car positioning device, movable on a trackway parallel to a track portion carrying railroad cars, has a carriage base and a pivoted car positioning arm to directly position a car within the dumper. This system uses a track parallel to a track on which the incoming rail cars reside. On this parallel track is an apparatus having a L-shaped arm that moves the cars on the rail car track.
U.S. Pat. No. 5,758,848 describes an automatic switching system integrated into freight cars that includes a microcomputer for controlling the automatic system and regulating the shunting speed, a rotary pulse generator for determining the shunting distance and freight car speed, distance sensors for detecting distance to and difference in speed relative to cars in front, an automatic coupling, a brake system for controlling the speed of the freight cars in the shunting zone and precise target braking on the sorting tracks and a data transmission device for information exchange with a superordinated control station. This system uses a device or devices on each freight car to control car speed when a car is humped. This gravity system also requires switches to function.
In U.S. Pat. No. 6,418,854, a new method for sorting railroad cars is presented, whereby outbound trains are built in proper standing order for departure directly on classification tracks using a continuously sustainable multi-stage sorting process. As described, single car sorting is efficiently performed at the hump, but one additional hump operation is required to replace the flat switching which is eliminated by this method. This system requires an additional hump to provide multi-stage sorting of rail cars. This gravity system also requires switches to function.
U.S. Pat. No. 7,596,433 describes a system for computing car switching solutions in a railway switch yard. Implementation of the system can be provided for the traditional switching mechanisms, e.g., the hump switch and the flat switch. This system uses a circular series of tracks and a hump to sort cars. It is a gravity system and also requires switches to function.
However, there still is a need to improve safety, cleanliness, efficiency and economy of switching cars from incoming trains to appropriate outgoing trains in a railroad yard.